Pillared clays, made from natural or synthetic clay, and their preparation are well known to the scientific literature. Because of the spacing between clay layers or sheets, i.e., the gallery height, provided by the pillaring material, these clays exhibit microporous properties making them useful in the preparation of various catalysts. Nevertheless, zirconia-pillared clays of reduced gallery height, i.e., less than about 8 Angstroms are unstable at temperatures above about 250.degree. C., particularly so at temperatures above about 300.degree. C., and the microporous qualities are destroyed or rendered inadequate for use as catalysts. Since a variety of processes, particularly hydroconversion processes, occur at temperatures above about 250-300.degree. C., pillared clays having the requisite stability are sought. This invention provides a method of preparing stable, reduced gallery height zirconia-pillared clays, useful in the preparation of catalysts for the hydroconversion of waxy feeds.